Series: Seattle's Great Viaduct Debate

As Seattle debates a deep-bore tunnel to replace the Alaskan Way Viaduct, Sightline examines the issue of potential cost overruns. The state legislature has made it clear it wants Seattle property owners on the hook—but the cost could be enormous. Read Sightline’s collection of posts on replacing the viaduct and what it means for Seattle residents.

A few months back, the transportation consulting firm NelsonNygaard released a fascinating report that looked at what might happen to downtown Seattle traffic patterns if the state builds a tunnel through downtown, while imposing a steep toll on drivers who choose to take it. (We've already written about that report once before.)
Below, for your viewing pleasure, is the most important image from that report. Click it to see a larger version -- and I'll explain what it means in a moment.
There's a lot of information in the chart, but you can ignore much of it. The only thing I want you to pay attention to are the orange and yellow bars:

Founded in 1993, Sightline Institute is committed to making the Northwest a global model of sustainability, with strong communities, a green economy, and a healthy environment. We work to promote smart policy ideas and monitor the region's progress towards sustainability.